Microwave dielectric characteristics of (Mg_0.95Ni_0.05)TiO₃-Ca_0.8Sm_0.4/3TiO₃ ceramic system

The microstructures and microwave dielectric properties of the (1 - x)(Mg_0.95Ni_0.05)TiO₃-xCa_0.8Sm_0.4/3TiO₃ ceramics system were investigated in the range of 0.1 ≦ x ≦ 0.9. The quality factor (Q × f value) and the temperature coefficient (τ_f) of the specimens were decreased with increasing Ca_0.8Sm_0.4/3TiO₃ content. The microstructures of (1 - x)(Mg_0.95Ni_0.05)TiO₃-xCa_0.8Sm_0.4/3TiO₃ ceramics were characterized using X-ray diffraction patterns and a scanning electron microscope (SEM). The areas of the various compositions in the ceramics were observed using energy dispersive spectroscopy (EDS), showing that Ca_0.8Sm_0.4/3TiO₃ coexists with (Mg_0.95Ni_0.05)TiO₃ in minor crystal grain. The existence of the Ca_0.8Sm_0.4/3TiO₃ phase can inhibit the abnormal grain growth of the (Mg_0.95Ni_0.05)TiO₃ phase. A relative permittivity (ε_r) of 22.9, a Q × f value of 92,000 GHz, and temperature coefficient of resonant frequency (τ_f) of -5.4 ppm/°C were obtained for 0.9(Mg_0.95Ni_0.05)TiO₃-0.1Ca_0.8Sm_0.4/3TiO₃ ceramics sintered at 1275 °C for 4 h.